My friend had this same problem when trying to join my server, however he could join some others. The "admin" and "webadmin" resources seem to disagree with his game. After disabling both of those resources he can now join and play as normal. The admin resource is DEFINITELY causing the problems here.. If I don't start them on the server launch he can play just fine, the instant I turn on the admin resource he gets network trouble. Also, if I stop the admin resource whilst he is still connected he stays with network trouble, but he can play fine again if he rejoins after I stop the admin resource. I have the admin resource included with the normal MTA 1.1 installer, not the one from the resources google code page.